Re: [PATCH 11/11] fs/ntfs3: Taking DOS names into account during link counting

From: Konstantin Komarov
Date: Tue Apr 23 2024 - 03:00:09 EST


On 18.04.2024 09:31, Johan Hovold wrote:
On Wed, Apr 17, 2024 at 04:10:59PM +0300, Konstantin Komarov wrote:
When counting and checking hard links in an ntfs file record,

  struct MFT_REC {
    struct NTFS_RECORD_HEADER rhdr; // 'FILE'
    __le16 seq;        // 0x10: Sequence number for this record.
>>  __le16 hard_links;    // 0x12: The number of hard links to record.
    __le16 attr_off;    // 0x14: Offset to attributes.
  ...

the ntfs3 driver ignored short names (DOS names), causing the link count
to be reduced by 1 and messages to be output to dmesg.
I also reported seeing link counts being reduced by 2:

[ 78.307412] ntfs3: nvme0n1p3: ino=34e6, Correct links count -> 1 (3).
[ 78.307843] ntfs3: nvme0n1p3: ino=5bb23, Correct links count -> 1 (2).
[ 78.308509] ntfs3: nvme0n1p3: ino=5c722, Correct links count -> 1 (2).
[ 78.310018] ntfs3: nvme0n1p3: ino=5d761, Correct links count -> 1 (2).
[ 78.310717] ntfs3: nvme0n1p3: ino=33d18, Correct links count -> 1 (3).
[ 78.311179] ntfs3: nvme0n1p3: ino=5d75b, Correct links count -> 1 (3).
[ 78.311605] ntfs3: nvme0n1p3: ino=5c708, Correct links count -> 1 (3).

- https://lore.kernel.org/all/Zhz_axTjkJ6Aqeys@xxxxxxxxxxxxxxxxxxxx/

Are you sure there are not further issues with this code?

For Windows, such a situation is a minor error, meaning chkdsk does not
report
errors on such a volume, and in the case of using the /f switch, it silently
corrects them, reporting that no errors were found. This does not affect
the consistency of the file system.

Nevertheless, the behavior in the ntfs3 driver is incorrect and
changes the content of the file system. This patch should fix that.
This patch is white space damaged and does not apply.

PS: most likely, there has been a confusion of concepts
MFT_REC::hard_links and inode::__i_nlink.
I'd also expect a Fixes and CC stable tag here.

And as this patch does not seem to depend on the rest of the series it
should go first (along with any other bug fixes).

Signed-off-by: Konstantin Komarov <almaz.alexandrovich@xxxxxxxxxxxxxxxxxxxx>
Johan

Hi Johan,

We are in the process of extending the tests for link counting and related scenarios.

If I find bugs, I'll reply ASAP.

Thanks for highlighting the bug.